Heat ¼ cup vegetable oil in a large wok or high-sided skillet over medium-high, swirling to coat bottom of pan, until glistening, about 1 minute. Crack 1 dried red chile (such as er jing tiao, bird chile, or chile de árbol) in half, add to wok, and cook, stirring, until fragrant, about 1 minute. Increase heat to high.
Add ½ medium head of cabbage (about 1 lb.), cored, cut into 1"–2"-long pieces, leaves separated, and cook, tossing constantly, until starting to brown, about 2 minutes. Sprinkle in 1½ tsp. Diamond Crystal or 1 tsp. Morton kosher salt and 1½ tsp. sugar and cook, tossing constantly and adjusting heat as needed if browning too quickly, until about a quarter of cabbage leaves are browned in spots, 2–3 minutes.
Reduce heat to medium, add 4 tsp. black (Chinkiang) vinegar and toss to combine. Taste and add up to another 1 tsp. vinegar if needed. Divide among plates to serve.
